An elevation is different. It shows the face of something, or perhaps more correct, the projection of an object/s to a plane. But my testing suggests it produces SECTIONS, not elevations.
Yes, you can use abbreviations in tables and figures. All abbreviations used in tables and figures should be defined in the table note or figure caption, respectively, even though the abbreviations will be also be defined in the text if they are used there.
Use em or px for font sizes. CSS inherited the units pt (point) and pc (pica) from typography. Printers have traditionally used those and similar units in preference to cm or in. In CSS there is no reason to use pt, use whichever unit you prefer.